1. Field of the Invention
The present invention relates to a peeling apparatus by which a layer including a structure, which is formed over a substrate, is peeled from the substrate. In particular, the present invention relates to a peeling apparatus used for manufacturing a semiconductor device, and a manufacturing apparatus of a semiconductor device for separating an element formation layer including a semiconductor element from a substrate used at the time of manufacture.
In the present invention, a semiconductor device for being manufactured includes a semiconductor element that can operate by utilizing semiconductor characteristics and a general device that operates by using a plurality of semiconductor elements.
As the semiconductor element, for example, a transistor, such as a MOS transistor or a thin film transistor, a diode, a MOS capacitor, and the like are given. In addition, the semiconductor device refers to an integrated circuit having a plurality of semiconductor elements, a device having a plurality of integrated circuits, a device having an integrated circuit and another element, or the like. The integrated circuit refers to, for example, a memory circuit such as a CPU, ROM, or RAM.
The device having a plurality of integrated circuits and the device having an integrated circuit and another element include, for example, a liquid crystal module substrate, a liquid crystal module using this module substrate, a liquid crystal display device using this module substrate, an EL (electroluminescence) module substrate, an EL module using this module substrate, an EL display device using this module substrate, an electronic appliance in which the liquid crystal module or the EL module is used as a display unit, an IC chip which is provided with an antenna and can communicate wirelessly, an electronic tag on which such an IC chip is mounted, an IC card, and the like.
2. Description of the Related Art
A technique has been developed in which after an integrated circuit is formed of a semiconductor element such as a TFT over a substrate such as a glass substrate or a quartz substrate, the integrated circuit is transferred from the substrate used for manufacturing the integrated circuit to a plastic film substrate. First, a step of peeling an integrated circuit from a substrate used for manufacture is needed in order to transfer the integrated circuit to another substrate. Thus, a technique has been developed by which an integrated circuit is peeled from a substrate.
For example, in Patent Document 1 (Japanese Published Patent Application No. H10-125931), the following peeling technique using laser ablation is described. A separation layer formed of amorphous silicon is formed over a substrate, a layer to be peeled which is formed of a thin film element is formed over the separation layer, and the layer to be peeled is bonded to an object to which the layer to be peeled is transferred, by a bonding layer. The separation layer is ablated by laser light irradiation, so that peeling of the separation layer is generated.
In addition, in Patent Document 2 (Japanese Published Patent Application No. 2003-174153), a technique is described in which peeling is performed by physical force such as that by human hands. In Patent Document 2, a metal layer is formed between a substrate and an oxide layer and peeling is generated at an interface between the oxide layer and the metal layer with the utilization of weak bonding of the oxide layer and the metal layer at the interface, so that the layer to be peeled and the substrate are separated from each other.
It has been known that when peeling is generated, electric charge is generated on surfaces of two separated layers and electrification is easily generated. This phenomenon is referred to as peeling electrification. Since the surfaces of two layers are close to each other at the moment of peeling, electric capacity is formed between these surfaces. When peeling proceeds, electric capacity is decreased with increase in a distance between the two layers; however, the amount of electric charge generated by peeling electrification is not changed, and thus, electric potential of the surface of the layer is increased inversely proportional to the electric capacity. When the electric potential of the surface of a peeled layer is increased, electric charge which is charged on the surface of the layer might be discharged toward inside the layer.
Accordingly, in the case where an object to be peeled is an integrated circuit, a semiconductor film, an insulating film, a conductive film, or the like is destroyed by melting due to heat generated by electric discharge. Consequently, a semiconductor element does not function in some cases. Even when the semiconductor element can operate without receiving a visible damage, a semiconductor or an insulator deteriorates due to high electric potential application and the semiconductor element does not show expected characteristics in some cases. Therefore, when electric discharge due to static electricity is generated, the semiconductor element is destroyed, or the integrated circuit itself using the semiconductor element does not operate normally due to characteristic deterioration in some cases.
Destruction of a semiconductor element or the like by electric discharge due to static electricity is referred to as electrostatic breakdown. Electrostatic breakdown is one of causes which drastically reduce yield. As a conventional method of avoiding electrostatic breakdown, there are a method in which electric discharge due to static electricity is tried not to be generated and a method in which damage to a semiconductor element caused by electric discharge is suppressed even when electric discharge due to static electricity is generated. As the former method, a method of removing generated static electricity by providing an ionizer in a semiconductor manufacturing apparatus is known. A typical example of the latter method is a method of manufacturing a protective circuit with a semiconductor element, and high electric potential generated by electric discharge can be prevented from being applied to a semiconductor element because of the protective circuit.
Even if static electricity is generated, electrostatic breakdown is not generated as long as electric discharge is not performed. Electric discharge is easily generated when electric potential difference between two objects is large. Therefore, an ionizer is an apparatus for supplying a positive ion and a negative ion to the air which serves as a path of electric discharge and for preventing generation of a large electric potential difference between the objects, as electric discharge is increased. However, since electric discharge due to peeling electrification is generated instantaneously when two layers are separated, electricity is not removed in time by an ionizer in some cases.
In addition, in the case of providing a protective circuit, when electric charge of electric discharge passes through the protective circuit, the protective circuit functions; therefore, destruction of a semiconductor element can be avoided. However, since surfaces of two layers to be separated are charged in peeling electrification, the electric discharge does not always pass through the protective circuit. Accordingly, in peeling electrification, electrostatic breakdown is not sufficiently prevented by the protective circuit.
For example, a method for preventing electric discharge due to peeling electrification is described in Patent Document 3 (Japanese Published Patent Application No. 2005-79395) (see Scope of Claims, Lines 42 to 48 in Page 9). Here, a conductive film is formed over a substrate, and a stacked body including a semiconductor element or the like is formed thereover. Peeling is generated at an interface between the substrate and the conductive film and electric charge generated at the time of peeling is diffused into the conductive film, so that destruction or characteristic deterioration of the semiconductor element due to charge is avoided.
However, in the peeling method of Patent Document 3, the conductive film remains in a lower part of the stacked body. Depending on an intended purpose of the stacked body, the conductive film becomes an obstacle and an expected intended purpose cannot be carried out due to the conductive film in some cases. In such a case, a conductive film is needed to be removed in the peeling method of Patent Document 3.